As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
VTK AND MAP SHOWED ON FO SIDE AT LEVEL OFF, AND SINGLE FMC OPERATION SHOWED IN FMC SCRATCHPAD. QRH CHECKLIST RESTORED DUAL FMC OPERATION. AT 20,000' ON DESCENT INTO SEA VTK AND MAP CAME BACK ON FO SIDE. GROUNDED - YES. REPLACED RIGHT FMC. OPS CHECK GOOD B737-800 AMM 34-61-02/201 AND AMM 34-61-00-710-801.